1. Field of the Invention
Diagnostic and prognostic methods involving measuring HMGB1 levels and/or antibodies specifically raised against HMGB1. Antibody- and drug-based methods for treating or reducing the severity of human immunodeficiency infection by modulating the activity of HMGB1.
2. Description of the Related Art
Early stages of HIV-1 infection are associated with local recruitment and activation of important effectors of innate immunity, NK cells and DCs. In the first hours and days of mucosal infection, HIV-1 crosses the epithelial barrier and infects CCR5-expressing DCs, macrophages and T cells in the mucosal tissues to initiate infection1,2. DCs express CD4, CCR5, DC-SIGN3 and other C-type lectin receptors (CLRs) that facilitate capture and dissemination of HIV-14,5. Immature DCs (iDCs) capture HIV-1 through CLRs6 and captured virus can be internalized and rapidly transmitted to nearby CD4 T cells, in the form of an infectious synapse7,8. DC-T cell conjugates facilitate productive infection in CD4 T cells9, and dissemination of the infection to the draining lymph nodes and subsequent other lymphoid tissue compartments is ensured by virus-carrying DCs together with infected macrophages and CD4 T cells10.
Migration of iDC to T cell area of secondary lymphoid tissues after virus uptake is associated to a maturation process that allows the resulting mature DC (mDC) to prime an antigen-specific response11. Recently, the fate of DCs has been found to be extremely dependent on autologous NK cells12. NK-iDC interaction results in activation of NK cells that, in turn, induces DC maturation or killing, depending on their respective density13,14,15. DC undergoing maturation secrete several cytokines, such as IL-12 and IL-18, that act as potent inducers of NK cell activation and cytotoxicity16,17,18,19,20. In turn, once activated, NK cells produce IFN-γ and TNF-α, capable of inducing DC maturation. This phenomenon is dependent on the engagement of NKp30 by ligands expressed on iDC17,21, and the down-regulation on iDC of HLA-E, the ligand for CD94/NKG2A inhibitory receptor22. Another mechanism was proposed suggesting that NK cells, activated by IL-18 released by iDC at the synaptic cleft, secrete HMGB1, which induces DC maturation and protects DCs from lysis20. HMGB1 is a nuclear protein that is present in almost all eukaryotic cells, and it functions to stabilize nucleosome formation, and acts as a transcription-factor-like protein that regulates the expression of several genes23,24. HMGB1 is released from necrotic cells, but it can also be secreted by activated macrophages25 and activated NK cells20 in response to inflammatory stimuli, and it is one of the main prototypes of the damage-associated molecular pattern molecules (DAMPs)26. It was recently discovered to be a crucial cytokine in the immune system, facilitating the trafficking of inflammatory leukocytes, and being critical for DCs to mature, reach the lymph nodes and sustain the proliferation of antigen-specific T cells, and to promote their polarization towards a T-helper 1 phenotype27,28.
The mechanisms involved in NK-DC interaction during viral infections are poorly understood. It was recently reported in murine CMV (MCMV) infection that MCMV-infected DCs were capable of activating syngeneic NK cells in vitro and also capable of enhancing NK-cell dependent clearance in vivo29, demonstrating the crucial role of NK-DC cross-talk in controlling viral replication. In HIV infection, NK-DC interaction was found defective in HIV-1-infected viremic, but not aviremic patients, characterized by abnormalities in the process of reciprocal NK-DC activation and maturation, as well as a defect in NK-cell elimination of iDCs30. The role of NK-DC cross-talk on maturation, function, and susceptibility to viral replication of HIV-1-infected iDCs was evaluated. It was discovered that maturation of HIV-1-infected DCs could be triggered by activated NK cells, but it was associated with a strong impairment of mature infected DCs to induce Th1 polarization following their crosstalk with NK cells. In addition, the cross-talk between NK cells and HIV-1-infected iDCs resulted in a dramatic increase in viral replication and proviral DNA expression in DCs. This process was mainly triggered by HMGB1, released both by NK cells and DCs, as a consequence of NK-DC cross-talk.
HIV-1 has evolved ways to exploit DCs, thereby facilitating viral dissemination and allowing evasion of antiviral immunity. The fate of DCs is dependent on NK cells. Below, the inventors detail the impact of NK-DC crosstalk on the fate of HIV-1-infected DCs. Activated NK cells efficiently triggered maturation of infected DCs, but this was associated with a strong impairment of mature DCs to induce Th1 polarization. Moreover, the crosstalk between NK cells and infected DCs resulted in a dramatic increase in viral replication and HIV-DNA in DCs. HMGB1 was crucial in this process, and inhibition of HMGB1 activity by glycyrrhizin or specific antibodies abrogated HIV-1 replication in DCs. The inventors describe how their new insights about how HIV ‘hijacks’ DCs to promote efficiently viral dissemination can provide new ways to inhibit HIV infection, new ways to diagnose and monitor HIV infection, new ways to monitor HIV infection, the viral load and the efficiency of treatment directed against HIV infection and new ways to carry out the prognosis of the state of progression of AIDS or towards AIDS.